New methyl pyruvate thiosemicarbazones and their copper and zinc complexes: synthesis, characterization, X-ray structures and biological activity

Abstract

By reacting thiosemicarbazides substituted on the aminic nitrogen with both alkyl or aryl groups, and methyl pyruvate a new group of methylpyruvate thiosemicarbazones (Hmpt) derivatives was obtained. These ligands were then treated with copper and zinc inorganic salts. All isolated compounds were characterized using spectroscopic methods. The single crystal structural analysis of the ligands Me–Hmpt·0.5H 2O 1, Et–Hmpt·H 2O 2, Ph–Hmpt 5, Meph–Hmpt 6 showed that only compound 6 presents significant deviation from planarity. The X-ray structure of [Zn(Me–Hmpt)Cl 2]·H 2O 8 showed that in this complex Me–Hmpt behaves as a neutral ligand SNO terdentate and that the penta coordination is achieved by chloride ions according to spectroscopic and elemental analyses. On the basis of the analytical data the same behavior is proposed for the other zinc complexes. All the ligands in copper complexes seem to be monodeprotonated; nevertheless the same SNO behavior is expected. Tests on cell proliferation of human leukemic cell line U937 showed that the copper complex Cu(Et–mpt)Cl·H 2O is the most active compound among those reported even though it is not able to induce apoptosis.